The invention relates to an oxygen breathing device, comprising an oxygen source, in particular a chemical oxygen generator or an oxygen pressure tank, at least one oxygen mask connected via an oxygen supply line to said oxygen source, a flow control unit adapted to receive a signal indicating ambient pressure or to detect ambient pressure and to control the flow of oxygen through the oxygen supply line depending on said ambient pressure, wherein the flow control unit is adapted to provide a low oxygen flow at a first ambient pressure, provide a higher oxygen flow at a second ambient pressure which is lower than said first ambient pressure and to increase said oxygen flow in at least two steps, preferably to increase said oxygen flow constantly.
A further aspect of the invention is a method for providing oxygen to a passenger of an aircraft and a method for maintaining an emergency oxygen system of an aircraft.
Generally, emergency oxygen supply systems for passengers of an aircraft are known. Such systems are used to supply oxygen to passengers in case of a pressure drop within the cabin or other emergency or critical situations, where the oxygen present in the cabin of the aircraft is not sufficient for the vital functions of the passenger within said cabin.
An emergency oxygen breathing device is known from the European patent application EP 2 143 469 A1. According to this reference, an oxygen breathing device provides oxygen flow from an oxygen source to an oxygen mask of a passenger or crew member. The oxygen flow is controlled by a control unit to ensure that the passenger is supplied with an exact amount of oxygen. The control unit receives pressure signals corresponding to the ambient pressure from a pressure sensor and temperature signals corresponding to the oxygen temperature passing through the breathing device from a temperature sensor. Generally, with such a device, it is possible to supply an amount of oxygen to a passenger in an emergency case which ensures that the passenger receives enough oxygen for maintaining all vital functions.
One important aspect of such oxygen breathing devices, however, is the desire to reduce the weight and the size of such devices in order to reduce the overall weight of the aircraft and to provide additional space for entertainment systems or the like. This size and weight reduction, however, shall not effect a reduction of the time period of supply of oxygen to a passenger. Accordingly, it is an object of the invention to provide an emergency oxygen system for passengers of an aircraft with reduced size and weight.
A further aspect of existing known assistance systems is the need to periodically maintain these systems and to adapt them to enhanced requirements or regulations in the aircraft industry. In the course of such maintenance it is a desire to be able to improve existing known oxygen systems in order to save weight and or space or to improve the characteristics of such systems in order to adapt them to existing requirements or regulations. It is a further object of the invention to provide a method and device which allows improvement of existing maintenance procedures in an efficient way.
It is another object to install modern oxygen masks which provide for low oxygen consumption at heights between 15,000 and 30,000 feet. Therefore, the oxygen flow at these heights needs to be adapted accordingly.
These and other objects are achieved by an oxygen breathing device according to the introductory function having an oxygen source, in particular a chemical oxygen generator or an oxygen pressure tank, at least one oxygen mask connected via an oxygen supply line to said oxygen source, a flow control unit adapted to receive a signal indicating ambient pressure or to detect ambient pressure and to control the flow of oxygen through the oxygen supply line depending on said ambient pressure, wherein the flow control unit is adapted to provide a low oxygen flow at a first ambient pressure, provide a higher oxygen flow at a second ambient pressure which is lower than said first ambient pressure and to increase said oxygen flow in at least two steps, preferably to increase said oxygen flow constantly, wherein a bypass valve is arranged in the oxygen supply line and comprises a first flow path and a second flow path comprising a bypass channel in a parallel flow arrangement to said first flow path, wherein said bypass valve is adapted to direct the flow of oxygen through said first flow path at an ambient pressure above a predetermined level according to a first flow condition and direct the flow of oxygen through said second flow path at an ambient pressure below a predetermined level according to a second flow condition, wherein said first flow path has a smaller flow cross section than said second flow path.
The oxygen breathing device provides for a weight saving means for life support of passengers in an aircraft. The device can be integrated in existing oxygen breathing systems without the need to redesign such existing systems. Moreover, the oxygen breathing device according to the invention is adapted to be used for currently used oxygen masks providing reduced oxygen consumption. Thereby, a reduced overall system weight can be achieved.
Preferably, the first ambient pressure is a system pressure corresponding to an altitude of the aircraft below 30,000 feet, e.g. intermediate altitudes between 15,000 and 30,000 feet. Still further it is preferred that the second ambient pressure is a system pressure corresponding to an altitude of the aircraft above 30,000 feet. The term smaller flow cross section reflects the fact that a smaller amount of oxygen per unit time can flow through the first flow path compared to the second flow path.